1. Field of the Invention
The present invention relates to a system and method for providing an uninterruptible power supply to a critical load. More particularly, the present invention relates to a system and method for providing N+2 redundancy and on-line maintenance capability in an uninterruptible power supply system with no single points of failure.
2. Discussion of the Related Art
Electric power pervades our world to such an extent that lack of it can lead to disaster, especially the financial, medical, and communications industries. As a result, standby and/or emergency power supply systems have been developed to answer the need for an uninterrupted supply of power. Typically, these so-called uninterruptible power supplies or supply systems are designed to handle a critical load during brief periods when service from a main power supply (e.g. a utility) becomes "interrupted" or unavailable. The critical load varies depending on the application and may, for example, include computer systems, communication systems, emergency lighting, life support systems, or anything whose continuous operation is necessary and/or whose interruption may prove disastrous.
Various uninterruptible power supplies have been developed and may include a battery backup system or a generator(s) for providing an alternate source of power. More complex systems may include transfer switches for selecting between alternate power sources and redundant feeds for providing alternate pathways to conduct power between the source(s) and the critical load. However, these conventional uninterruptible power supplies typically have a single point source of failure making them unsatisfactory for many important applications.
Other problems exist with respect to uninterruptible power supply systems, some of which are discussed in further detail below. A need exists for an improved uninterruptible power supply system that solves the problems described herein.